Airplanes often have an on-board gas turbine engine referred to as an auxiliary power unit that provides electrical power and compressed air to various systems throughout the airplane. When the airplane is on the ground, the auxiliary power unit is the main source of power to drive the environmental control systems, air driven hydraulic pumps, and the starters for the engines. Auxiliary power units may also provide pneumatic and electric power during flight.
In the aerospace industry there are specifications that govern the bounding of electrical cable or wires used on such engines. Honeywell International, which manufactures auxiliary power units, has a fairly typical aerospace specification AF 5483, Revision F for bounding the electrical cables of an auxiliary power unit. Referring to FIG. 1, this specification requires that a bundle 10 comprising a plurality of wires or cables shall be tied with a lacing material 12, per FIG. 1. If the bundle 10 comprises three cables or less, then the first wrap of the cord 12 must be around one of the cables and the second wrap of the cord 12 is around the entire bundle. If the bundle 10 comprises four wires or more, then the first wrap of the cord 12 must be around two adjacent cables and the second wrap of the cord 12 is around the entire bundle. The latter situation is shown in FIG. 1. Once the second wrap is complete, the ends of the cord 12 are secured by a clove hitch secured in a square knot or an anchor hitch as shown in FIG. 1. After trimming the loose ends, the ends of the cord 12 are further secured by saturating them with Humi-Seal, Type IB 15 or equivalent cement.
A typical auxiliary power unit requires, on average, about 105 ties. When assembling the harness, this bounding process is performed one hundred five times. The Applicant has found that it typically takes a skilled assembler about 11/2 minutes per tie to perform this bounding method using the cord 12 as set forth in the specification.
Accordingly, there is a need for wire bounding method that can be performed considerably faster than the prior art method. There is also a need for a cable tie that can be used in this improved method. Additionally, there is a need to eliminate the use of the Humi-Seal which is caustic and volatile.